This invention relates generally to DC power sources and is specifically directed to a DC power source capable of automatically accommodating either a 120 or 240 VAC input.
Most DC power sources are adapted to operate from a 120 volt AC line input. To permit the DC power source to operate from a 240 VAC line, a manual switch is generally provided for selecting either the lower or upper voltage mode of operation. It would be desirable to provide this dual voltage operating capability without requiring a manual switch operation on the part of the user. For example, the necessity to switch between different input voltage levels is easily overlooked and may result in damage to or destruction of an expensive component, device or system. The risk increases substantially where the DC power source energized by an AC line voltage is used to drive a sophisticated microcomputer terminal.
In addition, from a manufacturing standpoint it would be desirable to produce a DC power source capable of operating at either the conventional U.S. AC voltage of 120 volts or the 240 volt standard used generally throughout the rest of the world. A DC power source capable of accommodating both AC voltage levels without requiring operator intervention would also, in addition to eliminating the aforementioned over voltage hazards, eliminate the need for a manual switch in reducing the complexity of the power source.
The present invention affords the aforementioned advantages of an AC-energized DC power source which is equally compatible with both 120 or 240 VAC inputs in providing an automatic electronic switching arrangement to accommodate both input voltage levels.